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Can anyone diagnose my Craftsman air compressor issue?

jeeperguy21

NAXJA Forum User
Location
Syracuse, UT
My upright Craftsman air compressor (26 gallons) has worked flawlessly for the 9 or so years I've owned it. I went to fire it up today and it's like it won't kick into high gear. It kind of sputters and sometimes won't move at all and just hum. After a few tries, it fired up, but wouldn't do it again after stopping it and trying to restart. See the video:https://youtu.be/l7MNhnVXEuI

Anyone have any ideas? I haven't taken anything apart yet as I'm not sure what to look for once it's apart.
 
Check the start and run capacitors in the motor. A visual might show one ruptured, or disco the cap and measure with an ohmmeter. After it charges up, it should be almost infinite.
 
What old_man says sounds like a good start. Capacitors should be relatively inexpensive, but these oil less compressors are more or less disposable so start thinking about a new compressor.
 
Thanks, guys. I posted the same question on the DeLorean forum I belong to and I also got additional suggestions. Posting here for anyone experiencing a similar problem:

-Take the drain plug out of the tank and see if the compressor will run. If it does, the electric motor likely is weak and needs to be rebuilt or replaced.

-check that the water has been drained. There should be a drain on the bottom
- check that the air inlet/filter is not plugged up
- after unplugging the unit, take the black cover off the switch box and see if anything is loose.
 
Thanks, guys. I posted the same question on the DeLorean forum I belong to and I also got additional suggestions. Posting here for anyone experiencing a similar problem:

-Take the drain plug out of the tank and see if the compressor will run. If it does, the electric motor likely is weak and needs to be rebuilt or replaced.

-check that the water has been drained. There should be a drain on the bottom
- check that the air inlet/filter is not plugged up
- after unplugging the unit, take the black cover off the switch box and see if anything is loose.

The first one is pretty much what we are suggesting. If the capacitor(s) fail then it will be weak on power.

Water in the tank is not good but won't prevent the compressor from starting unless the tank is completely 100% filled with water. Unlikely.

In some cases the check valve in the tank can fail which means when he compressor starts its trying to start against tank pressure rather than unloaded. There is usually also an unloader mechanism. Typically a valve in the pressure switch which has a copper or plastic tube to the check valve. When the switch turns it off, you hear a hiss or blowoff. That's the unloader working. It allows loadless starting.
 
You should also be testing your over pressure relief valve, the brass valve with the ring on it next to the power switch. Pull it out (weekly) and air should exhaust out the tank. This is a good way to bleed out the tank pressure before opening up the drain on the bottom of the tank.

As others have stated, once the tank pressure is at zero, try the compressor pump again.

Tom
 
If you drain the tank and the motor starts every time then I think it is the one way valve in the output line. The motor can't start under the pressure of the tank without this valve working. It is usually an easy repair.
 
I used the compressor again yesterday (first time in months) and it performed flawlessly. I am sure it will start acting up again with more consistent usage, but I was pleased that it started, stopped, and started again without issue.
 
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